Figure 9

Adsorption cycles of (a) lead and (b) chromium of the L-Cyst-Fe₃O₄ NPs at 25 °C [adsorbate conc. = 50 mg/L; adsorbent conc. = 3.0 g/L]; desorption cycles of (c) lead and (d) chromium of the L-Cyst-Fe₃O₄ NPs at 25 °C [adsorbate conc. = 50 mg/L; adsorbent conc. = 3.0 g/L; desorption agent: 20 mL of 0.01 M HNO₃ and NaOH].